This invention relates to the field of circular knitting machines, and relates in particular to improvements to double cylinder circular knitting machines.
Double cylinder circular knitting machines and their operation are well known. They essentially comprise a lower cylinder part and an upper cylinder part which are coaxial and rotate together, a number of double hook needles placed in channels which coincide at the periphery of the two cylinder parts, sliders engaging the needles for selectively transferring these from one part of the cylinder to the other, cams to displace the sliders and, through these, to effect the operating movements of the needles and the yarn guides to feed the needles with each yarn which has to be knitted.
These double cylinder circular machines may have one or more feed stations and, with a suitable symmetrical arrangement of the cams at each feed station, can operate both with continuous rotary motion and alternating rotary motion according to the parts of an item which is being manufactured.
These machines are also normally equipped with scissors or with a yarn cutting-and-locking unit when a yarn has to be cut in the course of knitting and temporarily excluded from the work. The end of the cut yarn is then retained by the cutting-and-locking unit until the yarn is again taken up by the needles.
When knitting, the needles take the yarns from the corresponding yarn guides located at an intermediate level between the two lower and upper parts of the cylinder and perform rising and descending movements drawn by the corresponding sliders, which have to selectively follow working and resting courses determined by the corresponding control cams located around the double cylinder.
In particular, while knitting is in progress, the working needles at the point where the stitch is cast off are moved upwards by a lifting cam around the lower cylinder part (knit needles) and downwards by a cam around the upper cylinder part (purl needles). At the present time the said cams imparting movement, and therefore displacement of the needles to cast off the stitch, are substantially arranged corresponding to or in any event at a restricted distance from the yarn cutting-and-locking unit in a circumferential direction. This arrangement of the yarn cutting-and-locking units and the cams moving the needles through sliders according to the known art is illustrated for example in FIGS. 1, 3 and 4 of the drawings, in which arrow F indicates the direction of rotation of the double cylinder. Such needles 11xe2x80x2 and 23xe2x80x2 in the coruse of movement, sliders 12xe2x80x2 and 24xe2x80x2 connected to the said needles, yarn cutting-and-locking unit 13xe2x80x2, moving cams 14xe2x80x2 and 21xe2x80x2, needle tongue-guard cam 15xe2x80x2 and feed cam 16xe2x80x2 in association with sinker cams 17xe2x80x2 and 22xe2x80x2 will especially be noted in FIG. 1. FIGS. 3 and 4 show the position of a yarn guide 19xe2x80x2 in relation to needles 11xe2x80x2 and yarn cutting-and-locking unit 13xe2x80x2, were not working and when starting work respectively.
However, such a conventional arrangement of the parts of the machine may result in a disadvantage during knitting. In fact it can happen that when the yarn is subsequently picked up by the working needles the free end 20xe2x80x2 of the cut and retained yarn projects externally from the manufactured surface, and is therefore visible, thus in an unaesthetic position, the elimination of which requires manual intervention and drawing the end of the yarn towards the reverse side of the manufactured article, an operation which is awkward and time-consuming.
The purpose of this invention is to effectively overcome the disadvantage mentioned above, so that manufactured articles of better quality can be made on double cylinder circular machines without visible projecting pieces of yarn.
Another object of the invention is to eliminate the abovementioned disadvantage directly within the machine, by simple and efficient means which are capable of diverting the ends of the cut yarns in a more suitable direction so that they are hidden within the finished manufactured article.
The said objects and the advantages which derive therefrom are achieved in accordance with the invention by providing a double cylinder circular machine with a nozzle providing an air blast close to the yarn cutting-and-locking unit to divert the ends of the cut yarns held by the said unit towards the interior of the cylinder, that is onto the reverse side of the item being manufactured.
In order to create a space for physically fitting the nozzle in the vicinity of the yarn cutting-and-locking unit and to ensure that the air blast produced by the said nozzle is effective, the movement of the needles which have to cast off the stitch is delayed and displaced from this yarn cutting-and-locking unit in a circumferential direction. This is achieved by modification and repositioning of the cams moving the needles so that they are displaced a particular distance from the yarn cutting-and-locking unit as a result of the operation of these cams.